Flip-flop circuit for operating a switch



Nov. 4, 1952 R. B. BUCHNER FLIP-FLOP CIRCUIT FOR OPERATING A SWITCH Filed Feb. 15, 1949 SJZRHJVG VOZZ IGE I N V EN TOR. ROBERT .BZPTOLD BUCHNER BY &%

AGENI."

Patented Nov. 4, 1952 FLIP-FLOP CIRCUIT FOR OPERATING A SWITCH Robert Bertold Buchner, Eindhove'n, Netherlands,

assignor to Hartford NationalBank and Trust Company, Hartford, Conn., as trustee Application February 15, 1949, Serial No. 76,503

In the Netherlands April 26, 1948 3 Claims. (01. ire-1s) This invention relates to circuit-arrangements for use in automatic signalling systems, for example telephone systems, for energising a busy relay of a switch. In such systems, switches such as line finders and selectors are adjusted on a desired outlet under the control of a test device which either may be combined with a register or may form part thereof. In order to avoid that other switches may stop on the same outlet, the outlet concerned is made busy, during or after stopping of the switch, by varying the potential of a marking contact, for example by connecting the contact by way of the test line and the test device to earth.

Subsequently, the test device energises a relay associated with the switch and under the control of which the outlet is made permanently busy and various other functions are performed such, for example, as the through-connection of the energising lead of the stopping magnet, oi the test line and the operating lead of the relay.

In arrangements of known type, before the switch is adjusted, an auxiliary relay is first energised which prepares a holding circuit for itself in series with the winding of a second relay (busy relay), the second relay subsequent to the adjustment of the switch being operated due to the test device interrupting the circuit for energising the first relay, whereafter the said functions are performed by the second relay.

Furthermore, it is already known that, in order to economise relays, the busy relay may be energised directly from the control device by'supplying the relay with an energising pulse. The duration of such a pulse is fairly critical since, on the one hand, the pulse must be of a duration such that the relay is energised with certainty and, on the other hand, on account of the fact that the circuit through which the energizing pulse is supplied is through-connected by the relay to the outlet of the switch, it is possible in the case of a pulse of unduly long duration that a relay in a subsequent selecting stage may also be energised. Difilculties may arise in practice as a result of the fact that the operating time and the sensitivity of the different relays are different.

This disadvantage is met by the invention in that the pulse duration is matched to the operating time of the relay, the operation of the relay automatically stopping the current supplied to the arrangement through the test device. The invention exhibits the characteristic that during the adjustment of the switch, the relay-is included in an output circuit of a thermionic tube associated with the test device and in which the potential of a control electrode, upon the switch being stopped, is increased to such extent, that the tube is made conductive and the relay is energised, the potential at the moment at which the arm of a rest contact of the relay leaves its rest position being decreased to such extent that the tube is cut-off.

The said circuit-arrangement functions substantially without inertia since the pulse, instead of being stopped by the operation of a relay in the test device, is controlled by a thermionic tube.

The arrangement is preferably used in conjunction with a test device of the kind suggested in the copending patent application Serial No. 66,679, filed December 22, 1948, which comprises two tubes inter-connected in such manner that, when one tube is cut-off and hence non-conduc tive, the other tube is rendered conductive, and conversely and 'in which an electrode of that tube which is cut-off at the beginning of the test is connected to the test'arm of the switch. The operation of this test circuit is such that when the test arm of the switch strikes the contact of the desired outlet marked by a voltage, the cutoff tube is opened and the potential of the said contact is substantially reduced to the potential of corresponding contacts of other outlets. When the test circuit is interrupted, the said tube is again cut-off substantially without inertia. According to the invention, the tube of which an output circuit includes the relay is coupled to the other tubes in such manner that this tube is opened and cut-01f simultaneously with the tube which is cut-off at the beginning of the test, the last-mentioned tube being cut-01f by opening a rest contact of the relay in the test circuit.

The invention will now be explained more fully by reference to the accompanying drawing showing diagrammatically, by way of example, a line finder I circuit employing the arrangement according to the invention.

The figure shows two line finders 021 and 022, which are required to be adjusted in succession under the control of a test device OI.

According to the said suggestion, the test device OI'comp'rises two tubes B1 and B2, which are interconnected in such manner that, when one tube is cut-ofi, the other tube is rendered conductive, and conversely. To this end the anodes of B1 and B2 are connected by way of resistances '2 and 5-to a source of positive voltage and by way of voltage dividers '3, 4 and 6, I respectively to a source'of negative voltage, the control grids B1 and Bz-being connected respectively to a tapping on 'the voltage divider oi the other tube.

The resistances and potentials are chosen to be such that if tube B2 is conductive the control grid of B1 exhibits a negative potential with respect to the cathode such that B1 is cut-off and conversely. The cathode of tube Bi then has earth potential whereas the control grid exhibits a negative potential.

The cathode circuit of Br includes a highohmic resistance I, while the cathode may furthermore be connected by Way of an auxiliary contact N, a test line L3, and a break contact hi of a busy relay Hz of line finder Z2 to the test arm d of this switch. The test device also comprises two tubes B3 and B4 which serve to energise a busy relay H and rotary magnets D of the line finders respectively.

The winding of the rotary magnet D2 or 022 is included by way of a rest contact hz of relay H2 and a line L1 in the anode circuit of B4. When contact q is closed, the cathode of B3 is connected to a point of negative potential through a line L2, a rest contact ha and the winding of relay H2. The control grid of B3 is connected to the control grid of Bi and the control grid of B4 is connected to the control grid of B2. By a proper choice of the resistances and potentials it may be ensured that during the operation of the arrangement the tubes B3 and B4 are opened and cut-off simultaneously with the tubes B1 and B2 respectively.

At the rest position shown, the tubes B1 and B3 are cut-off and B2 is conductive. Tube B4 is still cut-off, contact I) being open, so that the screen grid of B4 is connected to earth potential.

The circuit-arrangement is put into operation by closing the contacts 17 b and q q respectively, which are associated with a relay l3 which is energized by a starting voltage applied thereto. The screen grid of B4 is thus connected by way of a resistance to the positive terminal of a battery so that B4 is made conductive and the rotary magnet D2 is energised. The switch 0212 now moves whilst the test device tests the outlets through the line L3, rest contact 722 and contact brush d. Th d contact of the desired outlet (point Q2) is, for example according to a method as described in the copending patent application Serial No. 86,872, filed April 12, 1949, characterized by a negative potential of, for example, 30 volts, the d contacts if the other outlets having earth potential. Consequently, as long as the contact arm (1 moves over contacts of non-desired outlets, the cathode of tube Bl is connected to earth potential and the tube remains cut-ofi. When the contact brush 11 reaches the marked contact, the potential of the cathode of tube Bl is reduced with respect to the potential of the control grids of B1 to such extent that the tube becomes conductive. Consequently, the potential of the control grids. of B2 and B4 decreases to such extent that the said tubes are cut-off. The disappearance of the energising current of rotary magnet D2 results in the switch 022 being stopped. At the same time the potential of the control grid of B1 increases due to the anode current of B2 being cut-off, so that tube B1 is opened still further and the voltage drop at the resistance l2 increases to such extent that the potential of the cathode substantially corresponds to earth potential.

The potential of the control grid of tube Bo also increases to such extent that tube 133 becomes conductive and relay H2 is energised in the circuit comprising the battery, winding H2, rest contact 71.2 line L2, contact q, cathode tube B3.

Relay H2 now attracts its armature. Working contact 71 2 closes a holding circuit for the relay from the negative terminal of the battery by way of the winding of H2, make contact 71.2 line L4, make contact a to earth. Contact 12.2 connects the d contact in the outlet of switch 0Z2 by way of switching brush (1, contact hz, line L4 and contact Q to earth, so that the out let is made permanently busy. The cathode of tube B1 is through-connected by working contact 712 to the test brush (1 of line finder 021 by way of contact b line L3, make contact hi switching arm 0 of 0Z2 and rest contact hi During the reversal of the switching arm of change-over contact 11.2 the following action takes place. As soon as the armature leaves its rest position and hence the cathode circuit of tube Bl which extends through rest contact M is interrupted, the anode current of tube B1 decreases to a small value as a result of the great voltage drop across resistance I. The anode potential of B1 and hence the potential of the control grid of tube B2 increases. Tube B2 becomes conductive so that the potential of the control grid of B1 is rendered negative to such extent that B1 is completely cut-off, while the control grid of tube B3 acquires a high negative potential. The test device has thus returned to the position which it occupied at the moment at which the device was made operative. This process is performed within an extremely short period.

In order to prevent the negative potential of point Q2 from returning for a short moment, which would involve the risk that a further switch might stop on a corresponding outlet, the construction of the relay must be such that contact 71.2 is closed before rest contact M is opened. The arms of the change-over contacts ha and 71.2 are reversed simultaneously with the armature of ha Make-contact hz connects the cathode of tube B3 to the winding of the busy relay H1 of line finder 0Z1. However, this relay is not energised since during the reversal of the armature the control grid of B4 has assumed a high potential.

Make-contact hz connects the anode of tube B4 to the winding of rotary magnet D1 of line finder 0Z1. The control grid of B4 during the operating period of relay H2 has assumed a potential'such that the tube is open at the moment at which make-contact hz closes.

Rotary magnet D1 is thus energised, whereafter line finder 021 is adjusted under the control of the test device in a manner similar to that above-described for line finder 0Z2.

What I claim is:

1. In an automatic signalling system entailing a plurality of lines of which a desired line presents a direct potential differing from that presented by the undesired lines, a test switch having outlet contacts connected respectively to said lines and a contact arm for successively engaging said outlet contacts, means including an electromagnet for driving said arm, a flip-flop circuit provided with cross-coupled first and second electron discharge tubes, said circuit having an initial quiescent condition in which said first tube is nonconductive and said second tube conductive and an operative quiescent condition in which said first tube is conductive and said second tube non-conductive, means coupled to the second tube of said flip-flop circuit responsive to the conduction of said second tube to energize said electromagnet and thereby drive said arm, means coupling said arm to said first tube to render said first tube conductive solely when said arm engages the outlet contact connected to said desired line, said first tube being biased to respond to said differing potential, a relay, means coupled to the first tube of said flip-flop circuit responsive to the conduction of said first tube to actuate said relay, said relay including first switching means which upon actuation connects the engaged outlet contact of said test switch to a potential point marking the line connected to the engaged outlet contact busy, and second switching means interposed between said arm and said first tube which upon actuation disconnects said arm from said first tube, whereby said first tube is rendered nonconductive.

2. An arrangement, as set forth in claim 4, wherein said means responsive to the conduction of said second tube to energize said electromagnet includes a third electron discharge tube having a cathode, a grid and an anode, means to apply a direct potential to said anode through said electromagnet, and means coupling said grid to said second tube to render said third tube conductive simultaneously with the conduction of said second tube and thereby energize said electromagnet. 3. An arrangement, as set forth in claim 5, wherein said means responsive to the conduction of said first tube to actuate said relay includes a grid controlled fourth electron discharge tube connected in series with said relay to a source of potential, the grid of said fourth tube being coupled to said first tube to render said fourth tube simultaneously conductive therewith.

ROBERT BERTOLD BUCHNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,794 Deakin Oct. 1, 1946 2,195,317 Martin Mar. 26, 1940 2,197,501 Holden Apr. 16, 1940 2,242,776 Clark May 20, 1941 2,354,682 Herbig Aug. 1, 1944 2,389,666 Herrick Nov. 27, 1945 

